Smart cards are devices having electronic elements in them such as electronic tags. By electronic tag is meant an assembly including a support, a communication circuit, such as a near-field communication circuit including an electronic chip and a near-field communication antenna, allowing contactless communication to be established with an external device for exchanging data. The antenna is generally connected to the electronic chip and is used not only as a means of contactless communication, but also to produce the energy needed for power supply to the chip.
In order to ensure optimal transmission of data between the tag and the external device, regardless of the tag's metallic environment, the tag is provided with a magnetic shielding layer that is capable of protecting the communication circuit. The protection of the circuit is important especially in a “contactless payment” application carried on a mobile telephone because the mobile telephone includes a battery and occasionally even a metal case which can interfere greatly with the quality of data transmission to an external reader when the tag is fixed to the mobile communication device.
A contactless type tag suited for application in a metallic environment is already known in the state of the art, in particular from document WO2008/065278. In this document, the tag includes an intermediate layer made of a magnetically hyper-conductive material, placed against a substrate bearing the antenna and the microcircuit. The assembly made up of the substrate, the antenna and the microcircuit is later embedded in a cover made of plastic by lamination or molding.
A disadvantage with known tags is that there is a need for accurate placement of the shielding layer so that it aligns with the communication circuit. Any misalignment means that there can be a reduction in the shielding, which with a contactless payment system could mean that the transaction could be compromised. Currently shielding is put in place by picking and placing the shielding material in a set location on a smart card. To do this requires accurate alignment of all components in the manufacturing process with little or no tolerances, which can be very difficult to achieve.
The present invention seeks to overcome the problems with the prior art by providing a method for accurately and easily positioning of a magnetic shield, which results in an improved smart card which is less likely to suffer from problems of interference when being used in a transaction. Furthermore, the flexibility of the method allows for the positioning of shielding material at a range of different locations on a smart card to the ease of positioning of the layer.